Some of the objectives of research at Carnegie are to understand the structural basis of gene regulation, to identify gene products that determine cell morphology, to describe and understand the cellular basis of neuronal regeneration and to understand the dynamic properties of membrane lipids. Electron microscopy plays a central role in these studies for analysis of nucleic acid arrangements and for localization of cellular constituents by cytochemistry and autoradiography. This proposal is to provide a new electron microscope to carry out these studies.